A system has been demanded in the field of photomechanical process which would provide photographic light-sensitive materials capable of reproducing an original with good properties and stable processing solutions or to simplify replenishing procedures in order to cope with diversity and complexity of printed matter.
For instance, an original in the step of photographing line subject may comprise a wide variety of images such as photocomposed characters, handwritten characters, illustrations, halftone dot photographs, which are all pasted on a common substrate. Therefore, such an original is composed of various images different from each other in density and line width. A process camera, a photographic light-sensitive material or an image forming process has been highly sought which provides good reproducibility of such originals. On the other hand, in making a printing plate for printing a catalog or a large-sized poster, enlargement (spread) or reduction (choke) of a halftone dot photograph is conventionally employed. However, in making a printing plate by enlarging halftone dots, line number becomes coarser resulting in photograph of unsharp dots. Whereas, in making a printing plate by reducing halftone dots, dots finer than those in the original and having a larger line number/inch than the dots in the original are photographed. Therefore, in order to maintain reproducibility of halftone gradation, an image forming process having greater capabilities has been desired.
As a light source in a process camera, a halogen lamp or a xenon lamp can be used. In order to obtain photographic speed for these light sources, the photographic light-sensitive materials to be exposed to these light sources are usually subjected to orthochromatic sensitization. However, orthochromatically sensitized photographic light-sensitive materials have been found to be more strongly influenced by chromatic aberration in the camera lens. Therefore, these photosensitive materials have a tendency to suffer deterioration of image quality. Further, this deterioration is more likely to occur in the instance of xenon lamp exposure.
As a system meeting the above mentioned demand for an image forming process having greater capabilities, a conventional process involves a lith silver halide light-sensitive material comprising silver chloride (containing silver chloride in an amount of at least 50%) with a hydroquinone developer having an extremely low effective concentration (usually 0.1 mol/liter or less) of sulfite ion for obtaining line images or halftone images with a high contrast and a high photographic density. However, this process has the defect that, since the sulfite ion concentration in the developer is low, the developer is extremely unstable against aerial oxidation. Therefore, in order to maintain stable development activity thereof, various efforts and techniques have been made to contend with this problem. However, processing speed is so slow due to these various efforts that a reduced working efficiency results.
Therefore, an image forming system has been desired which solves the problem of unstable image formation in the above described developing process (lith developing system) and which can provide ultra-contrasty photographic properties when developed with a processing solution having a good storage stability. As one system, a proposed process involves a surface latent image forming silver halide photographic material containing a specific acylhydrazine compound with a developer having a pH of 11.0 to 12.3, containing 0.15 mol/liter or more of a sulfite preservative and having a good storage stability to thereby form an ultra-contrasty negative image of a gamma of more than 10 as disclosed, for example, in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. This image forming system is characterized in that, while only silver chlorobromide having a high silver chloride content has been usable for conventional processes for forming ultra-contrasty images, it permits the use of silver bromoiodide or silver chlorobromoiodide.
The above described image forming system is excellent in that it provides sharp halftone dot quality, good processing stability, rapid processing speed and good reproducibility of an original. However, in order to cope with the diversity of recent printed matter, a system providing even more improved reproducibility of an original has been desired.
Towards this goal, it has already been proposed to achieve adequate working efficiency in gathering work and contact work by working under a brighter environment, and development of a plate making light-sensitive material capable of being handled in an environment of a substantially bright room and an exposing printer.
In the present invention, the light-sensitive material capable of being handled in a bright room means a light-sensitive material which can be safely used for an extended period of time under a light not containing ultraviolet component and having a wavelength of substantially 400 nm or longer as a safe light.
The light-sensitive material capable of being handled in a bright room and to be used in gathering work and contact work is a light-sensitive material, which is utilized for conducting negative image/positive image conversion or positive image/positive image conversion, by subjecting the light-sensitive material adapted for contact work to contact exposure using as an original a film having character image or halftone dot image formed by development processing. Such light-sensitive materials are required to possess:
(1) properties such that a halftone dot image and a line or character image can be converted from a negative image to a positive image according to the halftone dot area and line width or character image width, respectively; and PA0 (2) properties such that the tone of the halftone dot image and width of character or line image can be adjusted.
Light-sensitive materials capable of being subjected to contact work in a bright room have been proposed as such light-sensitive materials.
However, in a sophisticated image converting work of forming white-on-black character image by super-imposition contact work, the above mentioned conventional process by contact work in a bright room using light-sensitive materials adapted for being handled in a bright room has the drawback that, in comparison with a conventional process by contact work in a dark room using light-sensitive materials adapted for being handled in a dark room, a white-on-black character image with deteriorated quality results.
The process of forming a white-on-black character image by superimposition contact work is described in more detail below. As is shown in FIG. 1, a film (b) on which a character or line image is formed (line image original) and a film (d) on which a halftone dot image is formed (halftone dot original) are superposed on transparent or translucent stripping bases (a) and (c) (usually, polyethylene terephthalate films having a thickness of about 100 .mu.m), respectively, to prepare an original, and the halftone dot original (d) of this original is brought into a close contact with the emulsion surface of a light-sensitive material for contact work (e), followed by exposure of the assembly.
After the exposure, the light-sensitive material is subjected to development processing to form a white-on-black portion of line image in a halftone dot image.
In this process of forming white-on-black character images, it is ideal that negative image/positive image conversion can be conducted in accordance with halftone dot area of the halftone dot original and line width of the line image original. However, as is clear from FIG. 1, while the halftone dot original is directly brought into a close contact with the emulsion surface of the light-sensitive material for contact work upon exposure, the line image original (b) is spaced from the light-sensitive material by the stripping base (c) and the halftone dot original (d) upon exposure.
Therefore, when exposed in a sufficient amount to conduct negative image/positive image conversion with high fidelity, line width of white-on-black portion in the line image is narrowed because of out-of-focus exposure of the line image original (b) due to the presence of the spacer of the stripping base (c) and the halftone dot original (d).
JP-A-62-80640 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"), JP-A-62-235938, JP-A-62-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-296031, JP-A-63-314541 and JP-A-64-13545 disclose systems of using hydrazine for solving the above described problem. However, the systems are still insufficient, and more improved systems are desirable.
As an attempt to improve image quality, JP-A-61-213847, for example, discloses a process of silver-imagewise releasing of a development inhibitor from a carbonyl group-containing redox compound, and JP-A-64-72144, for example, discloses a process of silver-imagewise releasing of a development inhibitor from a hydrazine compound. The above described processes are effective in the instance of making halftone gradation less contrasty, but are insufficient in obtaining contrasty halftone dot image and low contrast halftone gradation for the purpose of obtaining a more contrasty image.
Therefore, it has been desired to develop a light-sensitive material which can provide a contrasty halftone dot image by using a stable developer and which permits tone control of image over a wide range.
In addition, in order to obtain contrasty halftone dot image, JP-A-56-106244, JP-A-61-230145, JP-A-62-211647, JP-A-63-503247, for example, disclose addition of amine compounds to a developer. However, developers containing these amine compounds are insufficient for the goal of enhancing stability of the developer or minimizing change in photographic properties due to the change in developer formulation (e.g., pH or sodium sulfite content).